1. Field of the Invention
The present invention relates to a scientific electronic calculator and, more particularly to a scientific electronic calculator for reading and displaying numeric values or expressions which are stored in the memories thereof.
2. Description of the Prior Art
With a conventional scientific electronic calculator for performing calculations by inputting numeric values, expressions and functions thereto, operations are performed not in the entry sequence of numeric values, expressions and functions, but by a predetermined priority of the function inputted. When the calculation of "-4.sup.2 " is to be performed, for example, the [-] key, [4] key, [X.sup.2 ] key, and [=] keys are sequentially depressed for entry in that order, as shown in FIG. 7(a), so as to provide the result "-16". The result "-16" was obtained by calculating 4.sup.2 first to provide "16" and then attaching the "-" sign preceding to "16", because the operation of square has priority over "-". In this case, the same result is obtained as that of the general numeric operation.
In addition to "-" and "4", the calculator also stores "-4" in its memory. When "-4" is read from the memory for display, the display exhibits "-4", which is also exhibited when the [-] and [4] keys are successively depressed.
When calculations are performed with the scientific electronic calculator having the aforesaid operational priority, different results may be produced depending on whether calculations are carried out by using numeric values read from the memory, or by using numeric values stored in the memory under a memory name, for the signs preceding to the numeric values may be treated differently in each case, depending on the operational priority of the function inputted. FIG. 7 shows a conventional method of displaying numeric values. By way of example, a case where "-4" is stored in the memory "A" as shown in FIG. 7(b) will be described.
There are two methods of squaring the memory "A". One is to utilize the memory name "A" for calculations. Here, the [A] key, [X.sup.2 ] key, and [=] key are successively depressed as shown in FIG. 7(c), resulting in 16. The other is to read the numeric value from the memory "A" for display and then perform calculations by using it. In this case, the [rcl] key, [A] key, [X.sup.2 ] key, and [=] key are successively depressed as shown in FIG. 7(d), resulting in -16. The [rcl] key here is for requesting the operation of reading a numeric value from a selected memory.
In the first method, A is treated as a whole variable so that "A.sup.2 " is displayed and that the numeric value stored in the memory "A" itself is squared in operations. In the second method, however, the successive entry of [rcl] and [A] reads out "-4" to be displayed, which is treated similarly to the case where the [-] key and [4] key are successively depressed. Consequently, calculations are carried out with the numeric expression -4.sup.2 displayed so as to provide the result "-16", because the square function, which is subsequently inputted by depression of the [X.sup.2 ] key, has priority over "-" in operation.
As described above, the conventional scientific electronic calculator is disadvantageous in that even if a numeric value stored in a memory is to be used to calculate a function, the result is sometimes different from the intended one because the calculator is so designed that numeric values or variables being displayed are used to calculate the function in accordance with a predetermined priority.
Japanese Unexamined Patent Publication No. 55-147747 discloses an electronic calculator which is constituted so that in performing calculations with parentheses, it displays left-hand parentheses "(" which are inputted via a left-hand parenthesis key upon entry of numeric expressions and which are the same in number as uncompleted operations.
Japanese Unexamined Patent Publication No. 53-106538 discloses a method of controlling the register of a calculator. The object of the invention is to effectively use the register for storing information on performing calculations with parentheses.